The present invention relates generally to a relatively large sized copying machine, e.g. a photomechanical camera, an electrophotographic copying machine and the like, and in particular to a device for confirming the position of an original image to be copied in such large sized copying machine.
Generally it is desirable for an operator to position an original which bears an original image to be copied thereon at a desired position in order to copy a desired image of the original accurately at a desired position of copying paper, e.g. paper sheet, photosensitive material or the like. However, it is difficult to do so, because the operator cannot confirm the position of the desired image of the original, which is turned down on an original holding plate of the copying machine.
It is well known such an apparatus as shown in FIG. 4, by which the operator confirms the position of an desired original image to be copied. In FIG. 4 there provided an exposure lamp 45 for exposing an original 43 which bears an desired original image to be copied onto a photosensitive material 47, and an auxiliary lamp 46 for confirming the position of the desired image through the original 43. These lamps 45 and 46 are alternatively switched over by means of a change-over switch 48 as an original pressing plate 44 is opened or closed. That is, the lamp 45 is lighted only when the photosensitive material 47 is positioned at a predetermined position on a conveyor 52, which is detected by means of a switch 49, and during the original pressing plate 44 is closed, which is in turn detected by means of a switch 48. On the other hand, the lamp 46 is lighted only when the original pressing plate 44 is opened for positioning the original on a transparent base plate 42 which is provided on a platform 41.
In such a known copying machine, the lamp 46 is designed so as to have such a light intensity as to transmit through the original 43. From such a view point, it may be desirable to use a lamp having a high light intensity, for the lamp 46. However, practically the lamp 46 uses such a lamp as having a less light intensity than that of the lamp 45, in order to avoid the damage of the base plate 42 and the original 43 caused by heat from the lamp 46, because it takes long for confirming the position of the original 43, while the lamp 46 is lighted.
In the above-mentioned known copying machine, the lamp 46 is placed apart from the optical pass between the original 43 and the photosensitive material 47, so that the original 43 placed on the base plate 42 is illuminated therefrom. As can be seen in FIG. 4, the optical system comprises the exposure lamp 45 which is movable relative to the original 43 immediately under the base plate 42, a mirror 51 provided under the base plate 42 and a lens 50 to the optical pass of which the photosensitive material 47 is positioned. The lamp 46 is placed not to interfere with the optical system. Thereupon, when the light intensity of the lamp 46 is reduced in order to avoid the problem caused by heat from the lamp 46, the light intensity thereof is apt to be insufficent at the center portion of the original 43, hence it is difficult to confirm the position of the desired original image especially in a large sized copying machine. On the other hand, in a copying machine of the type wherein an exposure lamp 45 is movable relative to the original 43 for exposing an original image onto a photosensitive material, such an auxiliary lamp as mentioned above stands in the exposure lamp's way, and thus it is difficult to provide the auxiliary lamp therein.